| Abstract
| - Thin films containing nanometer-sized PrAlO3 or NdAlO3 crystals evenly dispersed in anamorphous Al2O3 matrix were grown by chemical vapor deposition (CVD) of heterometalalkoxides, [Ln{Al(OPri)4}3(PriOH)] (Ln = Pr (1), Nd (2)). The lanthanoid to aluminum ratioin the precursors, established by single-crystal X-ray diffraction and chemical analyses ofthe crystalline products, enables the formation of a stoichiometric 1:1 composite of the generalformula LnAlO3/Al2O3 in a single-stage synthesis. The gas-phase thermolysis of 1 and 2 ina cold-wall reactor gave amorphous films of formal composition LnAl3O6, suggesting intactvaporization and decomposition of the heterometal frameworks on the substrates. On-linemass spectral analysis of the gaseous products formed during the CVD process revealedisopropyl alcohol, acetone, propene, and dihydrogen as the main byproducts. The electronspectroscopy for chemical analysis and energy-dispersive X-ray analysis confirmed the filmcompositions to be LnAl3O6, which was shown to be homogeneous through the film bulk byglow discharge mass spectrometry. The surface imaging (scanning electron microscopy/atomicforce microscopy) exhibits films with a regular globulated morphology. The annealing ofas-deposited films at 800 °C shows PrAlO3 and NdAlO3 to be the only crystalline phases(X-ray diffraction) with average grain sizes of 14 and 12 nm, respectively. The residual Alcomponent (Al2O3) remains amorphous until 1200 °C; however, the evolution of transitionaluminas (mixture of κ-, δ-, and γ-phases) was observed at higher temperatures (>1200 °C).The ceramic−glass (crystalline−amorphous) nature of the system was established by high-resolution transmission electron microscopy studies, while the compositions of the phaseswere determined by spatially resolved energy dispersive spectra. The infrared and solid-state 27Al MAS NMR data of the film material showed spectral patterns formed by anoverlapping of the signals corresponding to LnAlO3 and Al2O3 phases. The ellipsometricstudies revealed the refractive indices to be 1.76 and 1.67 for the Pr−O−Al and Nd−O−Alsystems, respectively. The film growth rates were found to be in the range 1.7−1.8 μm/h at500 °C.
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